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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><pre>SILVERTON HILLS FIELD BURNING FORECAST<o:p></o:p></pre><pre>OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE<o:p></o:p></pre><pre>9:00 AM PDT MON AUG 08 2011<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>BURN ADVISORY:<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Agricultural burning is not recommended.<o:p></o:p></pre><pre>Prep burning is allowed from 12:30pm to 5:00pm with a 50 acre limit. <o:p></o:p></pre><pre>Propane flaming is allowed from 12:30pm to 5:00pm. <o:p></o:p></pre><pre> <o:p></o:p></pre><pre><o:p> </o:p></pre><pre>WEATHER DISCUSSION:<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>In the upper atmosphere flow is very light with a weak trough off the Oregon and northern<o:p></o:p></pre><pre>California coastline. The morning ODF surface analysis shows onshore flow with a thermal<o:p></o:p></pre><pre>trough in the central valley of California and another thermally induced trough centered<o:p></o:p></pre><pre>in eastern Washington extending southward into central Oregon.<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>The morning Salem sounding showed a marine layer similar to yesterday - topping out<o:p></o:p></pre><pre>around 3500 feet. The cloud layer is much thinner, however, with bases around 1900 feet<o:p></o:p></pre><pre>and top sat about 2300 feet. The clouds should begin to breakup later this morning and<o:p></o:p></pre><pre>by noon expect mostly sunny skies. <o:p></o:p></pre><pre><o:p> </o:p></pre><pre>The morning sounding showed a more unstable atmosphere (compared to yesterday) above the<o:p></o:p></pre><pre>marine layer and with the weak trough offshore moving eastward there's a good chance of<o:p></o:p></pre><pre>isolated afternoon or evening thunderstorms over the southern and central Oregon<o:p></o:p></pre><pre>Cascades.<o:p></o:p></pre><pre> <o:p></o:p></pre><pre>The weather pattern is conducive to northerly winds all day and computer models show just<o:p></o:p></pre><pre>that: winds north or north-northeast through most of the transport layer then backing to<o:p></o:p></pre><pre>very light west-southwest at the top of the mixing layer and above. Conditions are not<o:p></o:p></pre><pre>favorable for good smoke evacuation to the east today. If any opportunity arose it<o:p></o:p></pre><pre>wouldn't be until early evening and then it would be marginal at best. <o:p></o:p></pre><pre><o:p> </o:p></pre><pre><o:p> </o:p></pre><pre>TODAY'S FORECAST:<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Morning clouds, mostly sunny by afternoon. Slight chance of thunderstorms over the<o:p></o:p></pre><pre>Cascades. <o:p></o:p></pre><pre>Salem's high temperature today will be near 80.<o:p></o:p></pre><pre>Relative humidity drops to 50% by 11am. Minimum relative humidity 35%.<o:p></o:p></pre><pre>Surface winds: N 4-7 mph slowly becoming NW 4-7 late afternoon or early evening.<o:p></o:p></pre><pre>Transport winds: N 5 mph slowly becoming NW 5-9 late afternoon or early evening.<o:p></o:p></pre><pre>Maximum mixing height: 4100 feet. <o:p></o:p></pre><pre>Sunset tonight: 8:29 pm <o:p></o:p></pre><pre> <o:p></o:p></pre><pre> <o:p></o:p></pre><pre>THREE-HOURLY DATA: <o:p></o:p></pre><pre> 11am 2pm 5pm 8pm <o:p></o:p></pre><pre> Temperature: 69 76 80 72 <o:p></o:p></pre><pre> Relative Humidity: 55% 40% 35% 46%<o:p></o:p></pre><pre> Surface Wind Direction: 350 340 330 290<o:p></o:p></pre><pre> Surface Wind Speed: 5 6 7 8 <o:p></o:p></pre><pre> Transport Wind Direction: 350 350 340 300 <o:p></o:p></pre><pre> Transport Wind Speed: 5 5 5 9<o:p></o:p></pre><pre> Estimated Mixing Height: 2800 3800 4100 1000<o:p></o:p></pre><pre> Ventilation Index: 14 19 20 9<o:p></o:p></pre><pre> <o:p></o:p></pre><pre>EXTENDED DISCUSSION:<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Forecast charts indicate Tuesday will be similar to today as a second weak upper level<o:p></o:p></pre><pre>trough moves in from the west. At this point computer models do not show any significant<o:p></o:p></pre><pre>switch to a more westerly transport flow with this feature. <o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Weak upper level ridging should limit the morning marine clouds later in the week, but a<o:p></o:p></pre><pre>northerly transport wind pattern will continue through the week for very limited, if any,<o:p></o:p></pre><pre>burn opportunities. <o:p></o:p></pre><pre><o:p> </o:p></pre><pre><o:p> </o:p></pre><pre>The National Weather Service’s digital forecast is available at:<o:p></o:p></pre><pre><a href="http://forecast.weather.gov/MapClick.php?lat=44.905&lon=-122.810">http://forecast.weather.gov/MapClick.php?lat=44.905&lon=-122.810</a>.<o:p></o:p></pre><pre> <o:p></o:p></pre><pre>Notes: <o:p></o:p></pre><pre>1. Mixing height, as used here, is the lowest height at which the <o:p></o:p></pre><pre> potential temperature exceeds the equivalent potential temperature <o:p></o:p></pre><pre> at the surface. As a practical matter it is the approximate height <o:p></o:p></pre><pre> to which a smoke plume will rise assuming good ignition, dry fuels, <o:p></o:p></pre><pre> and winds less than about 15mph. <o:p></o:p></pre><pre>2. Transport winds are a layer average through the mixing height, <o:p></o:p></pre><pre> weighted slightly toward the winds at the top of the layer. <o:p></o:p></pre><pre>3. Ventilation Index is the height of the mixing layer times <o:p></o:p></pre><pre> the transport wind speed divided by 1000. <o:p></o:p></pre><pre>4. Surface wind direction is the general expected wind direction. <o:p></o:p></pre><pre> At a specific point surface winds are highly dependent on <o:p></o:p></pre><pre> local terrain conditions.<o:p></o:p></pre><pre> <o:p></o:p></pre><pre>This forecast is provided under an agreement between the Oregon Department of<o:p></o:p></pre><pre>Agriculture and the Oregon Department of Forestry. For information contact ODA<o:p></o:p></pre><pre>at 503-986-4701. <o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Jim Little<o:p></o:p></pre><pre>ODF Meteorologist<o:p></o:p></pre><pre><o:p> </o:p></pre><pre><o:p> </o:p></pre><pre><o:p> </o:p></pre><pre><o:p> </o:p></pre><pre><o:p> </o:p></pre><pre><o:p> </o:p></pre><p class=MsoNormal><o:p> </o:p></p></div></body></html>